Hi, GtkStatusIcon (along with the whole "system tray" concept) has been deprecated in 3.14, so I'm not surprised that it starts breaking. On my desktop it's even worse: I can't see the icon anywhere at all. Still, as long as one single binary package includes both the backend and the applet, I think it's worth shipping the package in Stretch, as the backend is still useful in itself.
Regarding future plans, quoting what I wrote on https://bugs.debian.org/799942#24: "For the record, my plan is to add a GNOME Shell extension, and deprecate the old tray icon. Once this is done, I'll happily take good patches that port the old tray status applet to whatever interface is suitable for non-GNOME desktops these days. If this does not happen, there are great chances that I'll remove the old tray status applet at some point." I've started writing the aforementioned GNOME Shell extension back in June, but did not manage to complete it in time for Stretch, so I'm sorry that Stretch will include a poorly working applet :( … unless someone wants to try and complete that work in the next few days, in which case I'll happily share the initial skeleton I wrote in case it might help. Cheers, -- intrigeri